Tunisia's interim president Foued Mebazaa said he would step down after the Arab Spring's historic first election Sunday nine months after the toppling of strongman Zine el Abidine Ben Ali.

"I will recognise the results whoever wins and whatever the colour of the majority (in the future assembly)", Mebazaa told the Arabic language Assabah appearing Sunday.

"I shall hand over power to whoever is chosen by the constituent assembly as the new president of the republic," he said.

The Islamist Ennahda party is tipped to win the biggest bloc of ballots in Sunday's polls in which 7.2 million eligible voters are called to elect a 217-member assembly that will rewrite the constitution.

It will also have the loaded task of appointing an interim president and a caretaker government that will remain in place for the duration of the drafting process, expected to take a year.

"Sunday's elections may spring political surprises as they are the first pluralist, democratic elections since the revolution" that ousted Ben Ali after a 23-year reign, the interim president said.

"I am confident about the moderation of the Tunisian people and their leaders and I'm optimistic about the future of Tunisia and the smooth running of the elections," he added.

The election will be Tunisia's first-ever free elections with an Islamic party poised to win.

It comes nine months after the surprise toppling of strongman Zine el Abidine Ben Ali that sparked the Arab Spring.

From 7:00 am (0600 GMT), some 7.2 million eligible voters, many of them undecided to the end, can elect a 217-member assembly that will write a new constitution after decades of autocratic government.

The multi-party body will also have the loaded task of appointing an interim president and a caretaker government for the duration of the drafting process, expected to take about a year.

Ennahda, banned under Ben Ali, is polled to win the biggest bloc of votes in this first-ever open contest in a country where the outcome of elections used to be a foregone conclusion.

The constituent assembly will have to choose what type of government the country will have and how to guarantee basic liberties, including women's rights which many fear Ennahda would seek to diminish despite its assurances to the contrary.

Ennahda is accused in many quarters of being moderate in public but radical in the mosques.

The progressive left, however, remains divided with party leaders having failed to form a pre-vote alliance.

Ben Ali was ousted in January in a surprise, leaderless revolt that sparked region-wide pro-democracy uprisings which claimed their latest victim Thursday with the killing of Moamer Kadhafi of Libya, which will declare its official "liberation" Sunday as Tunisians go to the polls.

Unlike its neighbour, which descended into civil war, Tunisia's path to democracy has been mostly peaceful apart from some protests against the pace of transformation and sporadic violent outbursts by conservative Islamists against secularisation.

Elections chief Kamel Jendoubi on Saturday declared his ISIE polling commission "ready and confident", while the European Union observer mission said there was "almost no chance of cheating or falsifying results".

Ennahda had warned of a risk of vote rigging and vowed a fresh uprising if it detected fraud, but its leader Rached Ghannouchi stressed at a final rally Friday that the party would recognise the results "no matter Ennahda's score."

In what is widely regarded as the Arab Spring's first democratic test, Tunisians can choose from more than 11,000 candidates -- half of them women -- representing 80 political parties and several thousand independents.

Vote counting will start as soon as polling stations close at 7:00 pm, with results updated live throughout the night.